title: In vivo sodium (23Na) imaging of the human kidneys at 7 T: preliminary results.
abstract: OBJECTIVE
  To evaluate the feasibility of in vivo (23)Na imaging of the corticomedullary (23)Na gradient and to measure (23)Na transverse relaxation times (T2*) in human kidneys.
  
  
  METHODS
  In this prospective, IRB-approved study, eight healthy volunteers (4 female, 4 male; mean age 29.4 ± 3.6 years) were examined on a 7-T whole-body MR system using a (23)Na-only spine-array coil. For morphological (23)Na-MRI, a 3D gradient echo (GRE) sequence with a variable echo time scheme (vTE) was used. T2* times were calculated using a multiecho 3D vTE-GRE approach. (23)Na signal-to-noise ratios (SNR) were given on a pixel-by-pixel basis for a 20-mm section from the cortex in the direction of the medulla. T2* maps were calculated by fitting the (23)Na signal decay monoexponentially on a pixel-by-pixel basis, using least squares fit.
  
  
  RESULTS
  Mean corticomedullary (23)Na-SNR increased from the cortex (32.2 ± 5.6) towards the medulla (85.7 ± 16.0). The SNR increase ranged interindividually from 57.2% to 66.3%. Mean (23)Na-T2* relaxation times differed statistically significantly (P < 0.001) between the cortex (17.9 ± 0.8 ms) and medulla (20.6 ± 1.0 ms).
  
  
  CONCLUSIONS
  The aim of this study was to evaluate the feasibility of in vivo (23)Na MRI of the corticomedullary (23)Na gradient and to measure the (23)Na T2* relaxation times of human kidneys at 7 T.
  
  
  CONCLUSIONS
  • High field MR offers new insights into renal anatomy and physiology. • (23) Na MRI of healthy human kidneys is feasible at ultra-high field. • Renal (23) Na concentration increases from the cortex in the medullary pyramid direction. • In vivo measurements of renal (23) Na-T2* times are demonstrated at 7.0 T.
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany, stefan.haneder@umm.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Haneder
authors.forename: Vladimir
authors.initials: V
authors.lastname: Juras
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Michaely
authors.forename: Xeni
authors.initials: X
authors.lastname: Deligianni
authors.forename: Oliver
authors.initials: O
authors.lastname: Bieri
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Štefan
authors.initials: Š
authors.lastname: Zbýň
mesh_terms: D000328:Adult; D005240:Feasibility Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007668:Kidney / Q000033:anatomy & histology*; D007672:Kidney Cortex / Q000033:anatomy & histology; D007679:Kidney Medulla / Q000033:anatomy & histology; D016018:Least-Squares Analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011446:Prospective Studies; D012964:Sodium; D051598:Whole Body Imaging / Q000379:methods*; D055815:Young Adult
chemical_list: D012964:Sodium